Can Water Filters Remove Viruses? | What You Need to Know

Drinking water is often filtered prior to consumption, but have you ever considered what is being filtered out? Does filtration alone make drinking water safe by removing waterborne viruses, bacteria, and other contaminants? It’s something to consider, especially if you’re drinking from a natural water source.

Viruses cannot be removed by a standard water filter as they are too small. Most physical filters will remove contaminants that are on the micron scale. However, viruses are only nanometers (1-100 nm) in size and will pass through. Chemical filters, which bind contaminants to the filter’s surface, are also not designed to capture viruses.

There are, however, benefits to filtering your water, and there are simple methods for removing viruses to ensure your drinking water is safe.

The Effectiveness of a Household Water Filter

Physical filtration functions on the principle of size exclusion and are rated by their pore size. Typical household drinking water filters have a pore size of 1 micron, which means anything smaller than that will remain in the water following filtration.

Micron filters eliminate metals like zinc, copper, and mercury that have entered the water supply since leaving the water treatment plant. Often, the source of contamination is old water pipes in the system. These filters also remove most bacteria.

Filters that remove viruses are not practical

Ultrafiltration is possible using a nanometer-rated filter, and these would also remove viruses. However, these filters become clogged easily. Additionally, ultra or nano filters create enormous backpressure when trying to force a liquid through them, rendering their use in households impractical.

To increase the effectiveness of the micron-scale filters, their surface is often chemically modified, e.g., with activated carbon. These filters produce cleaner-tasting water through the removal of chlorine, sediment, and other organic compounds which adhere to the carbon surface. Unfortunately, viruses do not bind to these types of surface treatments and aren’t removed.

Removing Viruses from Water

To remove viruses from water, it needs to be purified. For most of us, this is performed by our local water treatment plant.

Typically, this is a four-step process, with the first three phases concerned with removing large particles and dirt:

1. Coagulation and Flocculation – Forcing particles to clump together to make them bigger and easier to remove
2. Sedimentation
3. Filtration
4. Disinfection – Normally involves adding sodium hypochlorite, which produces chlorine when dissolved in water. The chlorine then destroys the viruses, bacteria, and other pathogenic agents in the water.

How to remove viruses yourself

There are three main ways to remove viruses from water:

1. Boil It

You can, however, purify your water on your own. An effective method is to boil the water for at least one minute (or 3 minutes at high altitude). This prolonged, extreme heat is sufficient to destroy not only viruses, but bacteria, protozoa, and other pathogens as their proteins become denatured.

Once your water is boiled, it’s wise to keep it refrigerated until it’s needed to prevent any further contamination. Do note, though, boiling does not remove chemical toxins or other impurities, e.g., heavy metals or dirt. If possible, use a filter after boiling to enhance the quality of your drinking water.

2. Use Chlorine

If boiling isn’t an option, you can use chlorine to disinfect your water. Your household bleach will do, but only use unscented bleach that is marketed for disinfection or sanitization. You need only 2 drops of 6% bleach per quart of water. Note: this 6% on the bottle refers to the sodium hypochlorite concentration.

After adding the bleach, wait 30 minutes to allow the decontamination process to complete. If you can’t filter out the inevitable chlorine taste with an activated carbon filter, pour the clean water into another clean container and let it stand of a few hours to let the chlorine evaporate.

3. Use Iodine

Another option is to substitute the bleach for iodine solution, tablets, or crystals. For liquid iodine, you will need 5-10 drops per quart and leave for up to an hour. Iodine, however, isn’t recommended for long-term use and isn’t advised for people who are pregnant or have thyroid issues. Further, treating your water with iodine can cause diarrhea, stomach pain, and nausea.

Filters of the future might remove viruses

Technology is improving, and with it, small-scale, multi-stage filters are hitting the market. These models use a multistep process of filtration, activated carbon filtration, and then a 0.01-micron filtration to remove viruses. However, these triple filtration methods do not remove all viruses, and there is no guarantee that your water will be safe to drink.

Bottom Line

Each year, waterborne viruses account for 3.4 million deaths worldwide. The young are especially vulnerable, and this demographic accounts for 4,000 deaths per day. While most affected people live in the developing world, unsafe drinking water causes hundreds of hospitalizations each year in the United States and tens of deaths.

Health Consequences of Waterborne Viruses

Most waterborne viruses, including adenovirus, norovirus, and rotavirus, will result in gastroenteritis (aka, the stomach flu). Symptoms include diarrhea, vomiting, and fever which can be life-threatening depending on the patient’s pre-existing conditions, age, and access to virus-free fluids. Diarrhea alone is responsible for the deaths of 2.2 million people per year.

Many serious diseases/conditions can be contracted through contaminated water. These include hepatitis A and E, polio, SARS, conjunctivitis, myocarditis, malaria, cholera, meningitis, and paralysis. The long-term ramifications unsafe drinking water can have on your health are countless. Minimally, you will need a safe water supply and several weeks or months of recuperation if you contract a waterborne virus.

It’s only smart to take extra steps to make sure your water supply is safe. If in doubt, filter it then boil it.

Related Questions

How do viruses get into the water supply? Viruses often infiltrate the drinking water supply from human and animal urine or feces. This is frequently a consequence of unsanitary living conditions, which is why safe drinking water is a luxury in developing countries. In these areas, human waste is often disposed of into the same river that the population drinks from.

Does stream water have viruses? If an infected animal has died or defecated upstream, or a fellow human has contaminated the supply, you can easily contract a waterborne virus from naturally flowing water. The spread of viruses is commonplace at campsites, where poor personal hygiene can infect the drinking water. For these reasons, it’s recommended that you purify any water you drink, if possible.

For more, check out 8 Practical Ways to Purify Water Without Boiling It.